When a beverage is made in a process of conducting a fluid such as water through a quantity of extractable material, the characteristics of the beverage, including the taste, are determined by a number of parameters related to the process. For example, when the beverage is Espresso, a brewing pressure, a brewing time, a water temperature and a quantity of ground coffee in relation to a quantity of hot water which is conducted through the coffee are important parameters. In this context, a brewing pressure should be understood as the pressure of the hot water which is conducted through the coffee, which is determined by a flow through resistance of the coffee.
Usually, Espresso is made by means of an Espresso machine, which has a brew chamber for containing the coffee. When the Espresso machine is operated, water is heated and pumped through the brew chamber, wherein the hot water interacts with the coffee, as a result of which Espresso is obtained. In the process, it is important for the brewing pressure to reach a predetermined level, and to not get higher than that value, in order to have optimal extraction of the coffee.
Various methods for controlling the brewing pressure are known. For example, WO 01/74212 discloses a coffee-making device having a brewing chamber, wherein the brewing chamber comprises a cylinder in which a piston is capable of reciprocating. The coffee-making device is suitable for preparing different types of coffee, wherein a throughput pressure of water which is used in a process of making coffee is variable, so that it is possible to set a correct value of the pressure in any possible situation. In particular, the throughput pressure of the water is controlled by a shut-off valve which is arranged in a beverage outlet of the device, and which is capable of providing for various passages.